/*
 * Copyright (C) 2009 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.primitives;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkPositionIndexes;

import com.google.common.annotations.GwtCompatible;

import java.util.Arrays;
import java.util.Comparator;

/**
 * Static utility methods pertaining to {@code byte} primitives that interpret values as signed. The
 * corresponding methods that treat the values as unsigned are found in {@link UnsignedBytes}, and
 * the methods for which signedness is not an issue are in {@link Bytes}.
 *
 * <p>See the Guava User Guide article on <a
 * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>.
 *
 * @author Kevin Bourrillion
 * @since 1.0
 */
// TODO(kevinb): how to prevent warning on UnsignedBytes when building GWT
// javadoc?
@GwtCompatible
@ElementTypesAreNonnullByDefault
public final class SignedBytes
{
    private SignedBytes()
    {
    }

    /**
     * The largest power of two that can be represented as a signed {@code byte}.
     *
     * @since 10.0
     */
    public static final byte MAX_POWER_OF_TWO = 1 << 6;

    /**
     * Returns the {@code byte} value that is equal to {@code value}, if possible.
     *
     * @param value any value in the range of the {@code byte} type
     * @return the {@code byte} value that equals {@code value}
     * @throws IllegalArgumentException if {@code value} is greater than {@link Byte#MAX_VALUE} or
     *                                  less than {@link Byte#MIN_VALUE}
     */
    public static byte checkedCast(long value)
    {
        byte result = (byte) value;
        checkArgument(result == value, "Out of range: %s", value);
        return result;
    }

    /**
     * Returns the {@code byte} nearest in value to {@code value}.
     *
     * @param value any {@code long} value
     * @return the same value cast to {@code byte} if it is in the range of the {@code byte} type,
     * {@link Byte#MAX_VALUE} if it is too large, or {@link Byte#MIN_VALUE} if it is too small
     */
    public static byte saturatedCast(long value)
    {
        if (value > Byte.MAX_VALUE)
        {
            return Byte.MAX_VALUE;
        }
        if (value < Byte.MIN_VALUE)
        {
            return Byte.MIN_VALUE;
        }
        return (byte) value;
    }

    /**
     * Compares the two specified {@code byte} values. The sign of the value returned is the same as
     * that of {@code ((Byte) a).compareTo(b)}.
     *
     * <p><b>Note:</b> this method behaves identically to the JDK 7 method {@link Byte#compare}.
     *
     * @param a the first {@code byte} to compare
     * @param b the second {@code byte} to compare
     * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is
     * greater than {@code b}; or zero if they are equal
     */
    // TODO(kevinb): if Ints.compare etc. are ever removed, *maybe* remove this
    // one too, which would leave compare methods only on the Unsigned* classes.
    public static int compare(byte a, byte b)
    {
        return a - b; // safe due to restricted range
    }

    /**
     * Returns the least value present in {@code array}.
     *
     * @param array a <i>nonempty</i> array of {@code byte} values
     * @return the value present in {@code array} that is less than or equal to every other value in
     * the array
     * @throws IllegalArgumentException if {@code array} is empty
     */
    public static byte min(byte... array)
    {
        checkArgument(array.length > 0);
        byte min = array[0];
        for (int i = 1; i < array.length; i++)
        {
            if (array[i] < min)
            {
                min = array[i];
            }
        }
        return min;
    }

    /**
     * Returns the greatest value present in {@code array}.
     *
     * @param array a <i>nonempty</i> array of {@code byte} values
     * @return the value present in {@code array} that is greater than or equal to every other value
     * in the array
     * @throws IllegalArgumentException if {@code array} is empty
     */
    public static byte max(byte... array)
    {
        checkArgument(array.length > 0);
        byte max = array[0];
        for (int i = 1; i < array.length; i++)
        {
            if (array[i] > max)
            {
                max = array[i];
            }
        }
        return max;
    }

    /**
     * Returns a string containing the supplied {@code byte} values separated by {@code separator}.
     * For example, {@code join(":", 0x01, 0x02, -0x01)} returns the string {@code "1:2:-1"}.
     *
     * @param separator the text that should appear between consecutive values in the resulting string
     *                  (but not at the start or end)
     * @param array     an array of {@code byte} values, possibly empty
     */
    public static String join(String separator, byte... array)
    {
        checkNotNull(separator);
        if (array.length == 0)
        {
            return "";
        }

        // For pre-sizing a builder, just get the right order of magnitude
        StringBuilder builder = new StringBuilder(array.length * 5);
        builder.append(array[0]);
        for (int i = 1; i < array.length; i++)
        {
            builder.append(separator).append(array[i]);
        }
        return builder.toString();
    }

    /**
     * Returns a comparator that compares two {@code byte} arrays <a
     * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it
     * compares, using {@link #compare(byte, byte)}), the first pair of values that follow any common
     * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For
     * example, {@code [] < [0x01] < [0x01, 0x80] < [0x01, 0x7F] < [0x02]}. Values are treated as
     * signed.
     *
     * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
     * support only identity equality), but it is consistent with {@link
     * java.util.Arrays#equals(byte[], byte[])}.
     *
     * @since 2.0
     */
    public static Comparator<byte[]> lexicographicalComparator()
    {
        return LexicographicalComparator.INSTANCE;
    }

    private enum LexicographicalComparator implements Comparator<byte[]>
    {
        INSTANCE;

        @Override
        public int compare(byte[] left, byte[] right)
        {
            int minLength = Math.min(left.length, right.length);
            for (int i = 0; i < minLength; i++)
            {
                int result = SignedBytes.compare(left[i], right[i]);
                if (result != 0)
                {
                    return result;
                }
            }
            return left.length - right.length;
        }

        @Override
        public String toString()
        {
            return "SignedBytes.lexicographicalComparator()";
        }
    }

    /**
     * Sorts the elements of {@code array} in descending order.
     *
     * @since 23.1
     */
    public static void sortDescending(byte[] array)
    {
        checkNotNull(array);
        sortDescending(array, 0, array.length);
    }

    /**
     * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
     * exclusive in descending order.
     *
     * @since 23.1
     */
    public static void sortDescending(byte[] array, int fromIndex, int toIndex)
    {
        checkNotNull(array);
        checkPositionIndexes(fromIndex, toIndex, array.length);
        Arrays.sort(array, fromIndex, toIndex);
        Bytes.reverse(array, fromIndex, toIndex);
    }
}
